Alternating-current regulator.



No. 807,545. PATBNTED DEC. 19, 1905. G. PINZI.

ALTERNATING CURRENT REGULATOR.

APPLICATION FILED PEB.11,1904.

2 SHEETS-SHEET 1.

No. 807,545. PATENTED DEC. 19, 1905 G. PINZI.

ALTERNATING CURRENT REGULATOR.

APPLICATION FILED PEB.11.1904.

2 SHEETS-SHEET 2 M/ITNESSES //\7vE/vT0R @aau MMF GIORGIO FINZI, OFMILAN, ITALY.

ALTERNATlNG-CURRENT REGULATOR.

Specification of Letters Patent Patented Dec. 19, 1905.

' Application filed February 11, 1904. Serial No. 193,066.

To aZZ whom it may concern.-

Be it known that I, GIORGIO FINZI, electrical engineer, a subject of theKing of Italy, residing at 24 Piazza Oastello, Milan, in the Kingdom ofItaly, have invented certain new and useful Improvements inAlternating-Current Regulators, of which the following is aspecification.

In the regulation of electric circuits feeding the translating devicesthe change from one voltage to another is of frequent occurrence. Apartfrom those cases in which it is possible to effect the regulation of thevoltage at the source of current (regulation of the excitation) and fromthat in which the regulation is obtained at the cost of expenditure ofenergy (regulation by switching in resistances) the regulation both inthe case of continuous and alternating current may be obtained byinterrupting and closing the main circuit at suitable points; but bythis means the contact-surfaces are subjected to considerable attacks bythe sparks formed on the interruption of the main current. This defectis frequently overcome in switches (controllers) for electric vehiclesby means of the magnetic blow-outs, which, however, do not come intoquestion in the case of alternating currents, or by not permitting thecollector to leave one contactpiece until it has reached the next, bywhich means, although the interruption of the main circuit is obviated,still two contactpieces are momentarily short circuited, between whichthere exists a difference of potential.

The object of this invention is the employment on alternating-currenttransformers of a regulation of this latter kind in which nointerruption of the main circuit takes place, and the object has been tominimize the short-circuit current in such a manner that it cannotdetrimentally affect the transformer or cause sparking, which willattack the contactpieces, as when interruption takes place.

Upon constructional grounds it is not possible to multiply thegradations of voltage, and consequently the number of contactpieces adiafim'tum, as might otherwise ap pear to be desirable from thestandpoint of the diminution of the shortcircuit current. Further, it isnot possible simply to insert resistances between contact pieces and collectors such that even with a small number of gradations the desireddiminution of the short-circuit current may be obtained, because in thisway too much energy would be lost by heating. If, however, we are content with a smaller number of voltage gradationsiive, for exampleaswitch (controller) with five contact-pieces is obtained which by meansof connections presenting but very inconsiderable resistance may beconnected to suitable points of the transformer-winding, the saidconnections being calculated for being constantly traversed by the maincurrent. If now there are inserted between the said five main keys sixother auxiliary keys also connected with the intermediate points of thewinding by the intermediary of suitable resistances in such a mannerthat the brush will invariably remain in contact with two keys, (notmore and not less,) and if, further, matters are arranged in such amanner that the brush is not able to remain on one of the auxiliarykeys, but is conducted back to the main keys, it will be possible toproceed from one working voltage to the next without interrupting themain circuit without considerable loss by Joule effect and withoutproducing prejudicial short-circuiting currents. In doing this the saidresistances must be selected in such a manner that the shortcircuitcurrent (which is to pass through two such resistances in series apartfrom the moment at which a main and an auxiliary contact areshort-circuited) does not exceed a given strength and so that no notablefall of voltage takes place in the main current, which, according to theposi tion of the brush, will either traverse a single resistance of thiskind or two arranged in parallel. It should here be stated that theresistances are only traversed by the main current for short periodsseparated one from the other, so that in calculating them theirradiating-surfaces for heat does not come into consideration, but onlytheir heat capacity, so that in practice conductors of relatively smallcrosssection and also small longitudinal development may be employed. Itshould of course also be understood that the difference of voltagebetween two adjacent contacts should not exceed a given maximum value;otherwise the production of heavy sparking could not be avoided, howeverthe resistances inserted were calculated. Should the lowest voltageobtained in the distributing-circuit have a relatively high value withrespect to the "fall in voltage between two successive gradations of theswitch, it would be necessary in order to pass from the first main keyto zero to dispose of a large number of auxiliary keys. In this case itwould be better to interrupt the circuit directly by means of anordinary switch, the manipulation of which could be combined with thatof the handle of the keyswitch, (controller) In the accompanyingdrawings, Figure 1 illustrates diagrammatically a constructional form ofthe invention. a is a chokingcoil that is to say, one with a transformeror autotransformeracting as voltage equalizer and connected to thepoints I) and c of the line. The point 0 is directly connected to thetranslating device for example, the mo tor d. The conductors 6 proceedfrom suit able points of the choking-coil a to the main contact of thecollector. Between two successive main contacts f auxiliary contacts gare arranged. Upon these latter the brush h is not able to remain. Theyare in communication with intermediate points in the winding of thechoking-coil by means of resistances i. The brush is also incommunication with the other pole of the line. The switch 7c serves tointerrupt the input-conductor of the choking-coil when the brush liesupon the main key of the switch, which corresponds to the lowest workingvoltage.

Figs. 2 and 3 show a constructional form of the invention correspondingto the diagram in Fig. 1. Upon the upper end of a metal box is arrangedthe plate Z, of marble. Upon the under side of this plate are mountedthe following parts: A metal ring m, connected to the line; the fivemain keys which correspond to the five working voltages and which areconnected to the winding of the autotransformer by means of conductorsthe cross-section of which is calculated for the main current and whichproceed from the upper side of the plate Z; twenty-four auxiliary keysg, six of which are interposed between each two main keys and which arearranged outwardly relatively to these latter. These auxiliary keys areconnected by means of conductors, likewise proceeding from the upperside of the plate Z and of suitable resistance, to appropriate points ofthe winding of the autotransformer. A shaft n, driven by the crank 0,carries the brush 7b, which forms the connection between the ring m andeach one of the keysf and also temporarily between m and one of the keysg. By

means of the ratchet-wheel p, which is also mounted on the shaft n andwhich is submitted to the influence of the lever q, acted upon by thespring 1", the brush it is prevented from remaining on the auxiliarykeys 9, but is, 011 the contrary, compelled to remain constantly incontact with one of the main keys f. The shaft n is also provided with afinger s, ending in a vertical nose t.

By means of the fork u this nose actuates an oil-switch Q}, interposedbetween the ter1ni nals w a; of the autotransformer, and which onlyinterrupts the circuit when the collector comes into contact with themain key 1' of lowest potential. Upon the scale over which the handle 0slides the positions correspond ing to the five main keys and also tothe interruption of the circuit by the switchthat is to say, sixdifferent positions are indicated.

An apparatus of this kind may be utilized in all cases in which it isdesired to regulate the voltage of alternating currents along the line.It is especially applicable for use with single-phasealternating-current motors the velocity of which in their employment fordriving vehicles must be variable. In. the ease of motor-vehicles drivenby one or more motors the working voltage of which is intended to varywithin the ratio of one to two for example, between one hundred andtwohundred volts the regulation of which shouldbe possible both from thefront and rear platforms a switch (controller) of the kind describedabove would be extremely suitable. A switch of this kind should beprovided on each platform in connection with a transformer, each ofwhich is designed for one-half of the total outputthat is to say, forthe total current and for half of the necessary maximum voltage. Theprimary windings y of the two transformers should be arranged in series.The secondary windings 2 should be arranged in the manner indicated inthe diagram Fig. 4 or in some similar manner. The controller on. therear platform should be placed upon the key cor responding to themaximum voltagethat is to say, the lowest voltage required for runningthe motor, (one hundred volts in the foregoing example.) The higherpotentials (from one hundred to two hundred volts) and also theinterruption of the circuit would then. be effected by the manipulationof the controller on the front platform. If a single transformer is tobe provided, (for example, beneath the vehicle,) the procedure would besimilar, one half of its secondary winding being connected with each ofthe platform-controllers.

It will of course be understood that the switch described above mayequally well be employed with an ordinary transformer as with anautotransformer provided with a single winding; that the switch and thetransformer may constitute a whole or they may be separate; that theactuation may take place either by hand or by means of relays; that theinterrupter may be of any suitable kind or when the lowest workingvoltage is not far removed from zero it may be dispensed withaltogether, and, finally, that the method of regulation described isequally suitable for polyphase and for singlephase currents.

lIO

What I claim, and desire to secure by Letters Patent of the UnitedStates, is-

1. The combination of a switch having main and auxiliary keys with analternating current, variable voltage, non-sparking transformer, thewinding of the transformer being divided into a number of main divisionsthe ends of which are connected to said main keys by means of conductorsof low resistance;

said conductors; subdivisions of said main divisions, the ends of thesubdivisions being connected to auxiliary keys conductors of relativelyhigh resistance for said auxiliary keys; and a brush; whereby theshort-circuit current arising in the manipulation of the brush isdiminished.

2. The combination of a switch having main and auxiliary keys with analternating current, variable voltage, non-sp arking transformer, thewinding of the transformer being divided into a number of main divisionsthe ends of which are connected to said main keys by means of conductorsof low resistance; said conductors; subdivisions of said main divisions,the ends of the subdivisions being connected to auxiliary keys;conductors of relatively high resistance for said auxiliary keys; and abrush; whereby the short-circuit current arising in the manipulation ofthe brush is diminished; and means which prevent the brush fromremaining in permanent contact with the auxiliary keys.

3. In vehicles driven by alternating electric currents and having aplatform at each end, the combination of a switch, adapted for themaximum voltage which corresponds to the minimum working voltage andmounted on one platform; of a similar switch mounted on the otherplatform; and electrical connections, substantially such as described,between the two switches; and means which cause the switch that is inthe temporarily-rear platform to remain at said minimum voltage whilethe switch on the then front platform serves to effect the regulationbetween said voltage and the maxi mum working voltage and also the interruption of the circuit.

In testimony whereof I have hereunto set my hand, in presence of twosubscribing witnesses, this 15th day of December, 1903.

GIORGIO FINZI.

\Vitnesses:

H. P. SMITH, MIoIIELE H. DRAGO.

